微機電的揚聲器設計成用於優化聲壓與總諧波失真

MEMS Loudspeaker Design for Optimization of SPL and THD

謝亞欣(Shahin, Shadeeda)

指導教授 ： 渡邊浩志

國立交通大學/電機學院/電機資訊國際學位學程/碩士(2019年)

摘要

本論文的目的是研究提高微電子機械系統（MEMS）揚聲器性能的方法，該方法廣泛應用於助聽器和智能手機。對於助聽器，期望揚聲器的小型化以避免社會恥辱並且在聲音容易聽到時適合耳道內部。揚聲器的幾何形狀，特別是失真，也是一個主要問題，因為它對於有效的聲音再現是至關重要的。此外，非常小的揚聲器是智能手機不可或缺的單元，是當今通用的通信和娛樂設備。因此，強烈要求MEMS揚聲器在智能手機中產生優異的聲音質量。表徵揚聲器的主要因素是聲壓級（SPL）和總諧波失真（THD）。 SPL是與聲音音量相關的因素，因此需要更高的聲壓級。 THD是與噪聲相關的因素，因此需要較低的THD。換句話說，我們應該通過微調MEMS揚聲器的詳細設計來增加SPL並降低THD。在典型的MEMS揚聲器中，錐體是膜膜，其上連接有圓形線圈。磁性設備迫使圓形線圈通過洛倫茲力機械地移動，然後膜膜可以響應於到磁性設備的輸入信號而振動。膜膜的機械作用對圓形線圈的半徑和膜膜的厚度敏感。在本論文中，我們使用模擬器COMSOL Multiphysics Version 5. 3a通過調整圓形線圈的半徑和膜薄膜的厚度來改善圓柱形MEMS揚聲器的SPL和THD。圓形線圈的優化半徑為775μm，膜膜的最佳厚度為2μm。

關鍵字

微電子機械系統 ； 聲壓級 ； 總諧波失真 ； 洛倫茲力 ； 擴音器 ； 微電子機械系統揚聲器 ； 優化

並列摘要

The objective of this thesis is to study the method to improve the performance of Micro-Electro-Mechanical-Systems (MEMS) loudspeaker which is widely used in the application of the hearing aid and smart phones. For the hearing aid, the miniaturization of loudspeakers is desired to avoid social stigma and to fit inside the ear canal while the sound is easily heard. The geometry of loudspeaker, in particular, the distortion, is also a major concern since it is critical to efficient sound reproduction. Besides, very small loudspeakers are an indispensable unit of smart phones that are today’s universal communication and entertainment devices. Therefore, excellent quality of sound generated by MEMS loudspeaker in smart phone is strongly demanded. Major factors to characterize a loudspeaker are Sound Pressure Level (SPL) and Total Harmonic Distortion (THD). SPL is a factor related to the volume of sound and therefore higher SPL is desired. THD is a factor related to noise and thus lower THD is desired. In other words, we should increase SPL and decrease THD by fine-tuning the detailed design of MEMS loudspeakers. In a typical MEMS loudspeaker, the cone is a membrane film on which a circular coil is attached. A magnetic equipment forces the circular coil to mechanically move by Lorentz force and then the membrane film can be vibrated in response to input signal to the magnetic equipment. The mechanical action of membrane film is sensitive to the radius of the circular coil and thickness of the membrane film. In this thesis, we use a simulator, COMSOL Multiphysics Version 5.3a to improve SPL and THD of a cylindrical MEMS loudspeaker by tuning the radius of the circular coil and thickness of the membrane film. The optimized radius of the circular coil is 775

並列關鍵字

MEMS ； Sound Pressure Level ； Total Harmonic Distortion ； Lorentz Force ； Loudspeaker ； MEMS Loudspeaker ； Optimization

參考文獻

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[3]R. Sampaio, "MicroElectroMechanical Systems (MEMS) for applications in acoustics," Lisboa, Portugal, 2013.

[4]J. M. M. W. E. G. P. G. L. Iman ShahosseiniElie Lefeuvre, "Electromagnetic MEMS Microspeaker for Portable Electronic Devices," in DTIP Conference, Cannes, France , 2012.

[5][Online]. Available: https://www.technobotsonline.com/loudspeaker-100mm-25w-8-ohms.html.